With the gradual development of the domestic 3G network construction, the three major mobile communication operators all formally step into the 3G. However, currently, at the initial period of the construction of the 3G network and within the following development period, when compared with the 2G network which has went through a dozen years of continuous optimization and improvement, since the coverage level of the 3G network has a comparatively large gap with the 2G network with respect to the coverage breadth (e.g. the 2G network nearly covers all national natural villages) or the coverage depth (such as indoor places, basement and metro, etc.), all the major operators invariably take a long-term coexistence between 2G network and 3G network as their operation objective and policy. The China Mobile even raised the “three noes” principle, that is, no card changed, no number changed and no registration required, and a Time Division-Synchronous Code Division Multiple Access (TD-SCDMA)/Global System for Mobile Communication (GSM) dual-mode single-standby customized mobile phone terminal to promote and operate their own TD-SCDMA 3G network.
However, this policy of the coexistence between 2G network and 3G network, and the TD-SCDMA/GSM dual-mode single-standby terminal customization encounters problems in the real operation. On the one hand, since the existing policy of 2G and 3G dual-mode handover causes that abnormal failures such as frequent mobile phone terminal reselections, serious power consumption, call drops, network surfing stream interruption, and even off-network and so on happen occasionally, and user experience is comparatively worse; on the other hand, since the existing 3G network coverage quality is greatly inferior to that of the GSM network, which causes that the users lack confidence in the TD-SCDMA network. The problems of the network lead to the predicament of the terminal, and the predicament of the terminal conversely amplifies the problems of the network.